Nasal highflow improves ventilation in patients with COPD

Figures & data

Table 1 Demographic data

	(A) Pressure group (n= 19)	(B) Volume group (n= 18)	(C) pCO2 group (n=54)	P-value (A/B; B/C; A/C)
Age (years)	60.0±11.4	60.1±11.0	61.2±11.3	0.8; 0.2; 0.2
Sex ratio (women:men)	1:2.8	1:2.4	1:1.25	nd
BMI (kg/m^2)	23.4±4.5	23.3±4.7	23.9±5.7	0.9; 0.6; 0.7
FVC (% pred)	66.4±25.5	64.1±23.8	52.7±22.5	0.8; 0.06; 0.04
FEV1 (% pred)	42.9±23.5	41.4±22.0	35.1±18.6	0.8; 0.2; 0.2
FEV1/FVC (%)	52.0±13.3	51.4±12.6	51.0±13.6	0.9; 0.9; 0.8
Rtot (% pred)	233.8±121.4	242.6±125.8	331.4±197.3	0.8; 0.051; 0.054
TLC (% pred)	118.3±19.6	115.3±19.3	114.4±21.3	0.6; 0.9; 0.5
RV/TLC (% pred)	174.0±40.1	173.7±38.5	181.1±43.1	0.9; 0.5; 0.6
6-MWT (m)	220±117.6	212.9±109.2	196.9±134.4	0.9; 0.7; 0.6
Capillary pCO2 (mmHg)	49.1±11.5	48.0±12.1	58.2±13.8	0.8; 0.004; 0.02

Note: P-value calculation with Student’s t-test (two-sample).

Abbreviations: 6-MWT, 6-minute walk test; BMI, body mass index; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; nd, not done; pCO₂, partial pressure of CO₂; R_tot, total airway resistance; RV, residual volume; TLC, total lung capacity; pred, predicted.

Table 2 Mean airway pressure – medium prong size

	20 L/min	30 L/min	40 L/min	50 L/min	nCPAP (6 mbar)	nCPAP (10 mbar)	nBiPAP (14/6 mbar)
Mean (mbar) ± SD	0.92±0.49	1.44±0.78	2.14±0.98	3.01±1.03	4.96±1.34	8.56±2.02	7.46±1.77
P-value	<0.01	<0.03	<0.03	<0.03	<0.01	<0.01	>0.05

Notes: P-value to refer to zero in case of 20 L/min, in all other cases in comparison to previous applied device (for instance, P-value in nBiPAP describes no significant difference to nCPAP 10 mbar or for instance, a flow rate of 50 L/min increases mean airway pressure significantly compared to 40 L/min).

Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure; SD, standard deviation.

Figure 1 Changes in mean airway pressure (n=19, medium prong size).

Notes: *Significant P-value and **no significant P-value.
Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure.

Table 3 Changes in ventilatory parameters

	Spontaneous breathing	20 L/min	30 L/min	40 L/min	50 L/min	nCPAP (6 mbar)	nCPAP (10 mbar)	nBiPAP (14/6 mbar)
VT
Mean (mL) ± SD;	441.2±146.2	534.2±215.2;	523.7±228.5;	561.7±248.8;	558.8±260.0;	562.6±215.7;	579.3±262.6;	606.9±249.5;
mean (%) ± SD		104.9±21.4	113.3±27.6	123.2±27.7	123.8±27.2	125.3±29.4	126.8±28.8	133.6±30.1
P-value from mean (%)		<0.01	<0.05	<0.01	<0.01	<0.01	<0.01	<0.01
BR
Mean (bpm) ± SD;	15.7±4.1	11.6±3.6;	11.1±3.6;	10.3±3.3;	9.9±2.7;	14.3±3.8;	14.3±4.3;	15.4±4.3;
mean (%) ± SD		76.6±17.0	73.8±18.1	71.0±19.1	67.9±14.8	94.6±14.0	94.2±16.3	101.6±18.4
P-value from mean (%)		<0.01	<0.01	<0.01	<0.01	>0.05	>0.05	>0.05
MV
Mean L/min ± SD;	7.1±2.9	6.0±2.8;	5.6±2.6;	5.5±2.5;	5.4±2.5;	7.8±3.2;	8.2±3.8;	8.9±3.5;
mean (%) ± SD		86.6±14.2	83.3±21.1	85.3±24.0	83.7±24.7	117.7±32.2	119.9±28.6	133.7±36.2
P-value from mean (%)		<0.01	<0.01	<0.01	<0.01	0.01	<0.01	<0.01

Note: P-values in comparison to spontaneous breathing.

Abbreviations: BR, breathing rate; MV, minute volume–medium prong size; nCPAP, (nasal) continuous positive airway pressure; nBiPAP, (nasal) bilevel positive airway pressure; VT, tidal volume; SD, standard deviation.

Figure 2 Percentage changes in tidal volume (n=18, medium prong size).

Notes: *Significant P-value and **no significant P-value.

Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure.

Figure 3 Percentage changes in breathing rate (n=18, medium prong size).

Notes: *Significant P-value and **no significant P-value.

Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure.

Figure 4 Percentage changes in minute volume (n=18, medium prong size).

Notes: *Significant P-value and **no significant P-value.
Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure.

Table 4 RSBI – medium prong size

	Spontaneous breathing	20 L/min	30 L/min	40 L/min	50 L/min	nCPAP (6 mbar)	nCPAP (10 mbar)	nBiPAP (14/6 mbar)
BR/VT
Mean ± SD	41.6±22.0	27.4±17.9	28.0±18.9	25.1±19.9	25.4±18.3	32.8±28.3	32.3±26.5	32.3±23.3
Mean (%) ± SD		67.9±24.2	69.2±25.4	61.9±29.2	62.3±40.6	78.0±25.6	76.3±29.2	76.9±29.1
P-value from mean (%)		<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01

Note: P-value in comparison to spontaneous breathing.

Abbreviations: BR, breathing rate; nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure; RSBI, rapid shallow breathing index; VT, tidal volume; SD, standard deviation.

Figure 5 Percentage changes in RSBI (n=18, medium prong size).

Notes: *Significant P-value and **no significant P-value.
Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure; RSBI, rapid shallow breathing index.

Table 5 Comfort/dyspnea scale

	NHF small	NHF medium	NHF large	nCPAP	nBiPAP
Comfort scale (1–10)
Mean ± SD	4.3±1.5	3.4±1.5	3.9±2.0	5.4±1.9	4.4±2.4
P-value	<0.05		>0.05	<0.01	>0.05
Dyspnea scale (1–5)
Mean ± SD	2.7±0.7	2.6±0.9	2.6±0.9	3.2±0.7	2.8±1.1
P-value	>0.05		>0.05	<0.01	>0.05

Note: P-values in comparison to NHF with medium prong size.

Abbreviations: nBiPAP, (nasal) bilevel positive airway pressure; nCPAP, (nasal) continuous positive airway pressure; NHF, nasal highflow; SD, standard deviation.

Table 6 pCO₂ changes compared to baseline – medium prong size

	20 L/min	30 L/min
pCO2
Mean (%) ± SD	91±6.7	87.4±6.2
P-value in comparison to spontaneous breathing	<0.01	<0.01
P-value between different flow rates	<0.03

Note: P-values in comparison between different flow rates and baseline.

Abbreviations: pCO₂, partial pressure of CO₂; SD, standard deviation.

Figure 6 Percentage changes in pCO₂ after 2 hours of NHF breathing (n=54, medium prong size).

Note: *Significant P-value.
Abbreviations: NHF, nasal highflow; pCO₂, partial pressure of CO₂.